In this April 20, 2015 photo, David Cunnigham shows a prototype Tesla battery system that powers his Foster City, Calif. home. Cunnigham installed the battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Tesla is expected to unveil a stationary battery for homeowners and businesses on Thursday, April 30, 2015. (AP Photo/Jeff Chiu)

This April 20, 2015 photo shows a prototype Tesla battery system that powers the home of David Cunningham in Foster City, Calif. Cunnigham installed the battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Tesla is expected to unveil a stationary battery for homeowners and businesses on Thursday, April 30, 2015. (AP Photo/Jeff Chiu)

In this April 20, 2015 photo, David Cunningham points toward his SolarCity Web page, which details his solar energy output at his home in Foster City, Calif. Cunnigham installed a Tesla battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Tesla is expected to unveil a stationary battery for homeowners and businesses on Thursday, April 30, 2015. (AP Photo/Jeff Chiu)

In this April 20, 2015 photo, David Cunningham walks toward his solar panel-topped home, in Foster City, Calif. Cunnigham installed a Tesla battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Tesla is expected to unveil a stationary battery for homeowners and businesses on Thursday, April 30, 2015. (AP Photo/Jeff Chiu)

Observant Tesla fans noticed recently that there were no longer any mentions of the $3,500 10-kWh Powerwall on the Tesla website. That's usually how Tesla "announces" a change in its product line-up. The description of the Powerwall's capacity now simply says, "Each Powerwall has a 6.4 kWh energy storage capacity, sufficient to power most homes during the evening using electricity generated by solar panels during the day. Multiple batteries may be installed together for homes with greater energy needs."

A Tesla spokesperson told Greentech Media that the $3,000 7-kWh option is the only Powerwall left, because there's no demand for the bigger version:

We have seen enormous interest in the Daily Powerwall worldwide. The Daily Powerwall supports daily use applications like solar self-consumption plus backup power applications, and can offer backup simply by modifying the way it is installed in a home. Due to the interest, we have decided to focus entirely on building and deploying the 7-kilowatt-hour Daily Powerwall at this time.

Since Tesla introduced the Powerwall, it has said that the 10-kWh model could be used for about 500 charge-discharge cycles. That's not enough for the cost, some are speculating. The cheaper 7-kWh system wouldn't offer as much utility but the cost difference can still make it appealing to buyers. There's also the massive Powerpack for large-scale energy storarge needs.